The object of this invention is a lidded barrel for the storage and transportation especially of hazardous bulk materials in particulate, paste or liquid form, consisting of a cylindrical or cone-shaped lidded barrel body with an upper, radially asymmetrical barrel lid and a U-shaped clamping-ring closure which in the area of the upper barrel opening hooks under a flanged rim provided on the outer barrel wall while gripping the outer U-shaped rim of the barrel lid and, when in the closed position, pressing it against the barrel opening for a closure impermeable to gas and liquids, the barrel lid featuring between its flat top and its outer rim a circular groove (e.g. a groove for the grippers of barrel hoists) and at least one peripherally located, recessed bung well (i.e. bung enclosure) including, as the case may be, a bunghole with gas-tight and impermeable stopcap.
This invention is based on the realization that with this type of radially asymmetric barrel lid peripherally provided with at least one bung well and, as the case may be, a bunghole incorporated therein (for instance a 2" filling/draining bunghole on one side and/or a 3/4" venting/bunghole in the opposite peripheral area), the adjoining areas around the bung well or the transitions between the normal barrel-lid top level and the bung well are most vulnerable to impact, i.e. breakage-prone in the event the barrel is dropped and are the most likely to develop material overstress with attendant cracks and leaks. The same is true for barrel lids which are provided with bung wells but not with bungholes and fittings or spouts.
In cases of extreme stress such as internal-pressure tests, diagonal or lateral (side-wall) drop tests involving a barrel lid attached to a corresponding lidded barrel by means of a clamping ring, local overstress in the areas most strongly dented and thus most exposed to tensile stress plus substantial superimposed bending stress will cause these areas to be the first where the rim of the lid slips out of the upper part of the clamping ring, rendering the lidded barrel leaky. Especially barrel lids made of a thermoplastic material (hard plastic) will often crack and break in these areas even though they remain attached to the rim of the barrel body. The areas of the barrel lid which include the peripheral, recessed bung wells (perhaps even with a raised spout) are usually more rigid and inelastic than regular peripheral areas of barrel lids not containing bung wells.
A very significant reason for the breakage and cracking in the immediate area of the recessed bung well, addressed in this invention, is the presence in such radially asymmetric barrel lids of differentiated radial extensions or surface lengths. The radial extensions are measured from the center point of the lid to the upper, horizontally level edge of the outer inverted U-shaped rim of the lid that opens up toward the bottom. It is in these very recessed bung wells that the radial extensions are relatively shorter. This is true even more so in the case of barrel lids with a second circular corrugation which is interrupted by the bung enclosure. When there is an increased internal pressure, for instance in an internal-pressure test, shorter radial extensions in the area of the bung well will expose this area to greater stress (ovalization) and may cause a leak. The barrel lids as well as the lidded barrel bodies may consist of a thermoplastic material and/or metal (sheet iron).